If you like presenting your photos in a grid format "photos 1-9 of 83" then there's nothing missing. Once you step out of that mold there's unlimited possibility. Tabblo and ourdoings are two examples of mixing text and photos.
The fact that we still call them "photo sharing" sites shows how primitive our thinking is. What if you put all text-based web sites in one category?
What was missing for me that prompted ourdoings.com was a streamlined way to turn my backlog of photos into a nice summary of what my family had been up to. That's just my example. There are many other uses people might put photos to.
What I don't think we need is more social networking sites for photo enthusiasts. However, I could be proven wrong even for that specific category.
